Mixing Requirement for Static Tanks

With single component cryogenic liquids LIN, LOX, LA, etc. in VI tanks, under isochoric conditions, there is no storage instability problem from refilling with colder liquid, which will settle below the wanner heel. If mixing is not complete, the stratification of warm layer above cold layer will take place as normal during isochoric, zero-loss storage, when the tank contents pressurise as usual within the tank volume. 

However, with LNGs having different compositions as well as temperatures, it appears advisable that 100 % mixing practices are adopted during refuelling and refills, to prevent the initial formation of multiple layers of liquid. When the LNG is subsequently pressurised, with zero loss of vapour, there is then no chance of double-diffusive convection leading to spontaneous mixing and rollover between adjacent layers. 

This mixing practice appears to be a requirement for trouble-free storage of LNG under pressure. Complete 100 % mixing will, of course, ensure that normal hot-above-cold, two layer stratification will take place during pressurisation under stable convective conditions. 

however, well known that (a) sloshing of the tank contents is generated by accelerated motions of the road truck or ship and (b) sloshing will aid the mixing process. 

So this advisory provision on mixing practice may therefore only apply to static 

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